Preheat oven to 375°F (190°C) and line a baking sheet with parchment paper or lightly grease a loaf pan.
Combine breadcrumbs and milk in a small bowl; let sit for 5 minutes to hydrate.
In a large mixing bowl, combine the ground beef, ground pork, soaked breadcrumbs, egg, Parmesan, garlic, oregano, basil, salt, and pepper. Mix by hand until just combined.
Place approximately half of the meat mixture onto the prepared baking sheet, forming it into a flat rectangle roughly 1-inch thick.
Arrange the mozzarella strips down the center of the meat rectangle, leaving a 1-inch border around the edges.
Place the remaining meat mixture over the cheese and press the edges together firmly to seal the cheese completely inside the loaf.
Bake for 45 minutes.
Spread the marinara sauce over the top of the meatloaf and return to the oven for an additional 15 minutes, or until the internal temperature reaches 160°F (71°C).
Remove from oven and let the meatloaf rest for 10 minutes before slicing to prevent the cheese from running out.